The present invention relates to a method of controlling the operation of an air conditioning apparatus and an air conditioning apparatus controlled by this method, and more particularly, to a method and apparatus for controlling a cooling operation.
A conventional air conditioning apparatus is generally provided with a room temperature sensor such that a rotational speed of a compressor is controlled by the difference between an actual room temperature detected by the room temperature sensor and a target room temperature set by a user, whereby the room temperature is maintained at the target temperature. The rotational speed of the compressor is controlled in a PI (Proportional/Integration) control using the difference between the room temperature and the target room temperature and a changing rate of the room temperature.
In a cooling operation, the difference .DELTA.T1 between a room temperature and a target temperature is so large at the start-up time that a compressor is initially rotated at a maximum rotational speed, as shown in FIG. 1. For this reason, in the air conditioning apparatus, air is rapidly cooled down by a heat exchanger, so that a temperature of air discharged from the apparatus (a discharged air temperature) is rapidly cooled, whereby the room temperature is gradually lowered toward the target room temperature. When the room temperature comes close to the target room temperature, the rotational speed of the compressor is changed toward a minimum rotational speed by means of the PI control, and consequently the air conditioning apparatus is stably operated in vicinity of the target room temperature.
Meanwhile, the cooling operation of an air conditioning apparatus is performed in a manner so that cooled air thereby is discharged to a room to cool down the room, so that there may be a large difference between the actual room temperature and the discharged air temperature. For this reason, a person who is exposed to such cooled air blown from the air conditioning apparatus may feel chilly. Particularly, before the room temperature has reached the target room temperature, the difference between the room temperature and the discharged air temperature is extremely large.
Suppose, for example, that an actual room temperature is at 33.degree. C. and a target room temperature is set to 27.degree.C., as shown in FIG. 1. Then, the compressor is rotated at the maximum rotational speed with the start-up of the air conditioning apparatus, causing a discharged air temperature to abruptly drop to 14.degree.C., whereby the room temperature is gradually lowered toward the target value. At this time, the difference between the room temperature and the discharged air temperature is 19.degree. C. This means that a person, who has been accustomed to the room temperature of 33.degree. C., is subject to air blown at the discharged air temperature at 14.degree. C. which is 19.degree. C. less than the room temperature, and will suffer from an excessive chill. Subsequently, the discharged air temperature is raised as the room temperature is cooled down. However, the compressor still maintains its rotation at the maximum value, and therefore the discharged air temperature will be merely slightly raised. Since the difference between the room temperature and the discharged air temperature is still great, the person, if exposed to such discharged air, will feel chilly. When the room temperature has reached the target value set at 27.degree. C., the rotational speed of the compressor is dropped and operated so as to maintain the room temperature at the set target temperature. However, even in this situation, the discharged air temperature will be raised at most up to 18.degree. C., where the difference between the room temperature and the discharged air temperature is still about 9.degree. C. Therefore, the person, if exposed to a low temperature air for a long time, will suffer an unpleasant feeling or coldness.
As described above, with a conventional air conditioning apparatus, even if a target room temperature is set at a desired value, a temperature of a discharged air from the apparatus is significantly different from a room temperature, whereby blowing a low temperature air for a long time may result in spoiling a pleasant cooling feeling.